ESSENTIALS OF DIAGNOSIS
Noninflammatory blisters on sun-exposed sites, especially the dorsal surfaces of the hands.
Hypertrichosis, skin fragility.
Associated liver disease.
Elevated urine porphyrins.
Porphyria cutanea tarda is the most common type of porphyria. Cases are sporadic or hereditary. The disease is associated with ingestion of certain medications (eg, estrogens) and alcoholic liver disease, hemochromatosis, or hepatitis C.
Patients complain of painless blistering and fragility of the skin of the dorsal surfaces of the hands (Figure 6–29). Facial hypertrichosis and hyperpigmentation are common.
Porphyria cutanea tarda of hands in patient with darker skin. (Used, with permission, from Kanade Shinkai, MD.)
Urinary uroporphyrins are elevated twofold to fivefold above coproporphyrins. Patients may also have abnormal liver biochemical tests, evidence of hepatitis C infection, increased liver iron stores, and hemochromatosis gene mutations.
Skin lesions identical to those of porphyria cutanea tarda may be seen in patients who undergo dialysis and in those who take certain medications (tetracyclines, voriconazole, and NSAIDs, especially naproxen). In this so-called pseudoporphyria, the biopsy results are the same as those associated with porphyria cutanea tarda, but urine porphyrins are normal.
Barrier sun protection with clothing is required. Although the lesions are triggered by sun exposure, the wavelength of light triggering the lesions is beyond that absorbed by sunscreens.
Stopping all triggering medications and substantially reducing or stopping alcohol consumption alone may lead to improvement in most cases. Phlebotomy at a rate of 1 unit every 2–4 weeks will gradually lead to improvement. Very low-dose antimalarial medication (as low as 200 mg of hydroxychloroquine orally twice weekly), alone or in combination with phlebotomy, increases porphyrin excretion and improves the skin disease. Deferasirox, an iron chelator, can also be beneficial. Treatment is continued until the patient is asymptomatic. Urine porphyrins may be monitored.
Most patients improve with treatment. Sclerodermoid skin lesions may develop on the trunk, scalp, and face.
et al. Diagnostic and therapeutic strategies for porphyrias. Neth J Med. 2020;78:149.